What is the most energy efficient way to mechanically ventilate a home to bring in cool night air, after a hot day?

This is a well-insulated, two-sotry home with two gas furnaces, one for each floor, but not air conditioning, built 6 years ago. Standard construction techniques were used. Climate is temperate - San Francisco Bay Area. Due to security, noise, and particulate issues, sometimes it is not desirable to leave the windows open at night to cool the home, particularly the second floor. What options do we have, other than adding air conditioning?

This is a well-insulated, two-sotry home with two gas furnaces, one for each floor, but not air conditioning, built 6 years ago. Standard construction techniques were used. Climate is temperate - San Francisco Bay Area. Due to security, noise, and particulate issues, sometimes it is not desirable to leave the windows open at night to cool the home, particularly the second floor. What options do we have, other than adding air conditioning?

This is a great question that more people should think about before they install central air conditioning.